<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1" /><title>PairUtils xref</title>
<link type="text/css" rel="stylesheet" href="../../../../stylesheet.css" />
</head>
<body>
<div id="overview"><a href="../../../../../../../../../../apidocs/com/qrmedia/commons/collections/PairUtils.html">View Javadoc</a></div><pre>

<a name="1" href="#1">1</a>   <em class="comment">/*</em>
<a name="2" href="#2">2</a>   <em class="comment"> * @(#)PairUtils.java     24 Feb 2009</em>
<a name="3" href="#3">3</a>   <em class="comment"> * </em>
<a name="4" href="#4">4</a>   <em class="comment"> * Copyright © 2009 Andrew Phillips.</em>
<a name="5" href="#5">5</a>   <em class="comment"> *</em>
<a name="6" href="#6">6</a>   <em class="comment"> * This program is free software: you can redistribute it and/or modify</em>
<a name="7" href="#7">7</a>   <em class="comment"> * it under the terms of the GNU General Public License as published by</em>
<a name="8" href="#8">8</a>   <em class="comment"> * the Free Software Foundation, either version 3 of the License, or</em>
<a name="9" href="#9">9</a>   <em class="comment"> * (at your option) any later version.</em>
<a name="10" href="#10">10</a>  <em class="comment"> *</em>
<a name="11" href="#11">11</a>  <em class="comment"> * This program is distributed in the hope that it will be useful,</em>
<a name="12" href="#12">12</a>  <em class="comment"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</em>
<a name="13" href="#13">13</a>  <em class="comment"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</em>
<a name="14" href="#14">14</a>  <em class="comment"> * GNU General Public License for more details.</em>
<a name="15" href="#15">15</a>  <em class="comment"> *</em>
<a name="16" href="#16">16</a>  <em class="comment"> * You should have received a copy of the GNU General Public License</em>
<a name="17" href="#17">17</a>  <em class="comment"> * along with this program. If not, see &lt;<a href="http://www.gnu.org/licenses/" target="alexandria_uri">http://www.gnu.org/licenses/</a>>.</em>
<a name="18" href="#18">18</a>  <em class="comment"> */</em>
<a name="19" href="#19">19</a>  <strong>package</strong> com.qrmedia.commons.collections;
<a name="20" href="#20">20</a>  
<a name="21" href="#21">21</a>  <strong>import</strong> java.lang.reflect.Constructor;
<a name="22" href="#22">22</a>  <strong>import</strong> java.util.ArrayList;
<a name="23" href="#23">23</a>  <strong>import</strong> java.util.Collection;
<a name="24" href="#24">24</a>  
<a name="25" href="#25">25</a>  <strong>import</strong> com.qrmedia.commons.lang.ClassUtils;
<a name="26" href="#26">26</a>  
<a name="27" href="#27">27</a>  <em>/**<em>*</em></em>
<a name="28" href="#28">28</a>  <em> * Utility methods for {@link Pair Pairs}.</em>
<a name="29" href="#29">29</a>  <em> * </em>
<a name="30" href="#30">30</a>  <em> * @author anph</em>
<a name="31" href="#31">31</a>  <em> * @since 24 Feb 2009</em>
<a name="32" href="#32">32</a>  <em> *</em>
<a name="33" href="#33">33</a>  <em> */</em>
<a name="34" href="#34">34</a>  <strong>public</strong> <strong>final</strong> <strong>class</strong> <a href="../../../../com/qrmedia/commons/collections/PairUtils.html">PairUtils</a> {
<a name="35" href="#35">35</a>  
<a name="36" href="#36">36</a>      <em>/**<em>*</em></em>
<a name="37" href="#37">37</a>  <em>     * Creates pairs by &amp;quot;pairing-up&amp;quot; each object in a collection with the same</em>
<a name="38" href="#38">38</a>  <em>     * partner object.</em>
<a name="39" href="#39">39</a>  <em>     * </em>
<a name="40" href="#40">40</a>  <em>     * @param &lt;U>   the type of the first object in the pair</em>
<a name="41" href="#41">41</a>  <em>     * @param &lt;V>   the type of the second object in the pair</em>
<a name="42" href="#42">42</a>  <em>     * @param firstObjects  the objects to become the first objects in the pairs</em>
<a name="43" href="#43">43</a>  <em>     * @param secondObject  the object to be paired with all the &lt;code>firstObjects&lt;/code></em>
<a name="44" href="#44">44</a>  <em>     * @return a collection of pairs containing an entry in &lt;code>firstObjects&lt;/code> and </em>
<a name="45" href="#45">45</a>  <em>     *         &lt;code>secondObject&lt;/code></em>
<a name="46" href="#46">46</a>  <em>     * @see #toPairs(Class, Collection, Object)        </em>
<a name="47" href="#47">47</a>  <em>     */</em>
<a name="48" href="#48">48</a>      <strong>public</strong> <strong>static</strong> &lt;U, V> Collection&lt;Pair&lt;U, V>> toPairs(Collection&lt;? <strong>extends</strong> U> firstObjects, 
<a name="49" href="#49">49</a>              V secondObject) {
<a name="50" href="#50">50</a>          <strong>return</strong> toPairsInternal(<strong>null</strong>, firstObjects, secondObject);
<a name="51" href="#51">51</a>      }
<a name="52" href="#52">52</a>      
<a name="53" href="#53">53</a>      <em>/**<em>*</em></em>
<a name="54" href="#54">54</a>  <em>     * Creates pairs of the given pair subclass by &amp;quot;pairing-up&amp;quot; each object in a </em>
<a name="55" href="#55">55</a>  <em>     * collection with the same partner object.</em>
<a name="56" href="#56">56</a>  <em>     * &lt;p></em>
<a name="57" href="#57">57</a>  <em>     * Expects the subclass to have a two-argument constructor, taking the first</em>
<a name="58" href="#58">58</a>  <em>     * and second objects as arguments. The constructor does &lt;u>not&lt;/u> need to be visible.</em>
<a name="59" href="#59">59</a>  <em>     * </em>
<a name="60" href="#60">60</a>  <em>     * @param &lt;T>   the type of the pair subclass to be returned</em>
<a name="61" href="#61">61</a>  <em>     * @param &lt;U>   the type of the first object in the pair</em>
<a name="62" href="#62">62</a>  <em>     * @param &lt;V>   the type of the second object in the pair</em>
<a name="63" href="#63">63</a>  <em>     * @param firstObjects  the objects to become the first objects in the pairs</em>
<a name="64" href="#64">64</a>  <em>     * @param secondObject  the object to be paired with all the &lt;code>firstObjects&lt;/code></em>
<a name="65" href="#65">65</a>  <em>     * @return a collection of pairs containing an entry in &lt;code>firstObjects&lt;/code> and </em>
<a name="66" href="#66">66</a>  <em>     *         &lt;code>secondObject&lt;/code></em>
<a name="67" href="#67">67</a>  <em>     * @throws IllegalArgumentException </em>
<a name="68" href="#68">68</a>  <em>     *              if &lt;code>pairClass&lt;/code> is &lt;code>null&lt;/code> or if the given subclass cannot </em>
<a name="69" href="#69">69</a>  <em>     *              be instantiated using the expected two-argument constructor</em>
<a name="70" href="#70">70</a>  <em>     * @see #toPairs(Collection, Object)</em>
<a name="71" href="#71">71</a>  <em>     */</em>
<a name="72" href="#72">72</a>      <strong>public</strong> <strong>static</strong> &lt;T <strong>extends</strong> Pair&lt;U, V>, U, V> Collection&lt;T> toPairs(Class&lt;T> pairClass,
<a name="73" href="#73">73</a>              Collection&lt;? <strong>extends</strong> U> firstObjects, V secondObject) {
<a name="74" href="#74">74</a>          
<a name="75" href="#75">75</a>          <strong>if</strong> (pairClass == <strong>null</strong>) {
<a name="76" href="#76">76</a>              <strong>throw</strong> <strong>new</strong> IllegalArgumentException(<span class="string">"'pairClass' may not be null"</span>);
<a name="77" href="#77">77</a>          }
<a name="78" href="#78">78</a>          
<a name="79" href="#79">79</a>          <strong>return</strong> toPairsInternal(pairClass, firstObjects, secondObject);
<a name="80" href="#80">80</a>      }    
<a name="81" href="#81">81</a>      
<a name="82" href="#82">82</a>      <strong>private</strong> <strong>static</strong> &lt;T <strong>extends</strong> Pair&lt;U, V>, U, V> Collection&lt;T> toPairsInternal(Class&lt;T> pairClass,
<a name="83" href="#83">83</a>              Collection&lt;? <strong>extends</strong> U> firstObjects, V secondObject) {
<a name="84" href="#84">84</a>          
<a name="85" href="#85">85</a>          <strong>if</strong> (firstObjects == <strong>null</strong>) {
<a name="86" href="#86">86</a>              <strong>return</strong> <strong>new</strong> ArrayList&lt;T>();
<a name="87" href="#87">87</a>          }
<a name="88" href="#88">88</a>          
<a name="89" href="#89">89</a>          Collection&lt;T> pairs =  <strong>new</strong> ArrayList&lt;T>(firstObjects.size());
<a name="90" href="#90">90</a>          
<a name="91" href="#91">91</a>          <strong>for</strong> (U firstObject : firstObjects) {
<a name="92" href="#92">92</a>              
<a name="93" href="#93">93</a>              <strong>try</strong> {
<a name="94" href="#94">94</a>                  pairs.add(toPair(pairClass, firstObject, secondObject));
<a name="95" href="#95">95</a>              } <strong>catch</strong> (InstantiationException exception) {
<a name="96" href="#96">96</a>                  <strong>throw</strong> <strong>new</strong> IllegalArgumentException(exception.getMessage());
<a name="97" href="#97">97</a>              }
<a name="98" href="#98">98</a>              
<a name="99" href="#99">99</a>          }
<a name="100" href="#100">100</a>         
<a name="101" href="#101">101</a>         <strong>return</strong> pairs;
<a name="102" href="#102">102</a>     }
<a name="103" href="#103">103</a>     
<a name="104" href="#104">104</a>     <em>/**<em>*</em></em>
<a name="105" href="#105">105</a> <em>     * Creates a pair.</em>
<a name="106" href="#106">106</a> <em>     * </em>
<a name="107" href="#107">107</a> <em>     * @param &lt;U>   the type of the first object in the pair</em>
<a name="108" href="#108">108</a> <em>     * @param &lt;V>   the type of the second object in the pair</em>
<a name="109" href="#109">109</a> <em>     * @param firstObject the first object in the pair, may be {@code null}</em>
<a name="110" href="#110">110</a> <em>     * @param secondObject the second object in the pair, may be {@code null}</em>
<a name="111" href="#111">111</a> <em>     * @return a pair consisting of the first and second object</em>
<a name="112" href="#112">112</a> <em>     */</em>
<a name="113" href="#113">113</a>     <strong>public</strong> <strong>static</strong> &lt;U, V> Pair&lt;U, V> toPair(U firstObject, V secondObject) {
<a name="114" href="#114">114</a>         <strong>try</strong> {
<a name="115" href="#115">115</a>             <strong>return</strong> toPair(<strong>null</strong>, firstObject, secondObject);
<a name="116" href="#116">116</a>         } <strong>catch</strong> (InstantiationException exception) {
<a name="117" href="#117">117</a>             <strong>throw</strong> <strong>new</strong> AssertionError(<span class="string">"Unable to create normal Pair?!? "</span> 
<a name="118" href="#118">118</a>                     + exception.getMessage());
<a name="119" href="#119">119</a>         }
<a name="120" href="#120">120</a>     }
<a name="121" href="#121">121</a>     
<a name="122" href="#122">122</a>     <em class="comment">//if pairClass is null a "normal" pair will be generated</em>
<a name="123" href="#123">123</a>     @SuppressWarnings(<span class="string">"unchecked"</span>)
<a name="124" href="#124">124</a>     <strong>private</strong> <strong>static</strong> &lt;T <strong>extends</strong> Pair&lt;U, V>, U, V> T toPair(Class&lt;T> pairClass, U firstObject, 
<a name="125" href="#125">125</a>             V secondObject) throws InstantiationException {
<a name="126" href="#126">126</a>         
<a name="127" href="#127">127</a>         <strong>if</strong> (pairClass == <strong>null</strong>) {
<a name="128" href="#128">128</a>             
<a name="129" href="#129">129</a>             <em class="comment">// in this case, T == Pair&lt;U, V></em>
<a name="130" href="#130">130</a>             <strong>return</strong> (T) <strong>new</strong> Pair&lt;U, V>(firstObject, secondObject);
<a name="131" href="#131">131</a>         }
<a name="132" href="#132">132</a>         
<a name="133" href="#133">133</a>         <em class="comment">// attempt to instantiate the given class, expecting one two-argument constructor</em>
<a name="134" href="#134">134</a>         <strong>try</strong> {
<a name="135" href="#135">135</a>             <strong>return</strong> getPairConstructor(pairClass).newInstance(firstObject, secondObject);
<a name="136" href="#136">136</a>         } <strong>catch</strong> (Exception exception) {
<a name="137" href="#137">137</a>             
<a name="138" href="#138">138</a>             <em class="comment">/*</em>
<a name="139" href="#139">139</a> <em class="comment">             * Convert all of the possible exceptions (Instantiation, NPE if no constructor exists</em>
<a name="140" href="#140">140</a> <em class="comment">             * etc. to an InstantiationException.</em>
<a name="141" href="#141">141</a> <em class="comment">             */</em>
<a name="142" href="#142">142</a>             <strong>throw</strong> <strong>new</strong> InstantiationException(<span class="string">"Unable to instantiate instance of "</span>
<a name="143" href="#143">143</a>                     + pairClass.getSimpleName() + <span class="string">" due to "</span> + exception.getClass().getSimpleName() 
<a name="144" href="#144">144</a>                     + <span class="string">": "</span> + exception.getMessage());
<a name="145" href="#145">145</a>         }
<a name="146" href="#146">146</a>         
<a name="147" href="#147">147</a>     }    
<a name="148" href="#148">148</a> 
<a name="149" href="#149">149</a>     <em class="comment">//@SuppressWarnings("unchecked")</em>
<a name="150" href="#150">150</a>     <strong>private</strong> <strong>static</strong> &lt;T <strong>extends</strong> Pair&lt;?, ?>> Constructor&lt;T> getPairConstructor(Class&lt;T> pairClass) 
<a name="151" href="#151">151</a>             throws NoSuchMethodException {
<a name="152" href="#152">152</a>         <em class="comment">/*</em>
<a name="153" href="#153">153</a> <em class="comment">         * Will throw a NoSuchMethodException if one of the pair types could not be resolved, and</em>
<a name="154" href="#154">154</a> <em class="comment">         * if no matching constructor can be found, of course.</em>
<a name="155" href="#155">155</a> <em class="comment">         */</em>
<a name="156" href="#156">156</a>         Constructor&lt;T> constructor = pairClass.getDeclaredConstructor(
<a name="157" href="#157">157</a>                 ClassUtils.getActualTypeArguments(pairClass, Pair.<strong>class</strong>).toArray(<strong>new</strong> Class&lt;?>[] {}));
<a name="158" href="#158">158</a>         
<a name="159" href="#159">159</a>         <strong>if</strong> (!constructor.isAccessible()) {
<a name="160" href="#160">160</a>             constructor.setAccessible(<strong>true</strong>);
<a name="161" href="#161">161</a>         }
<a name="162" href="#162">162</a>         
<a name="163" href="#163">163</a>         <strong>return</strong> constructor;
<a name="164" href="#164">164</a>     }
<a name="165" href="#165">165</a>     
<a name="166" href="#166">166</a> }
</pre>
<hr/><div id="footer">This page was automatically generated by <a href="http://maven.apache.org/">Maven</a></div></body>
</html>

